Leiomyomas are benign monoclonal proliferations of uterine smooth muscle cells occurring in one of every three women of reproductive age. Twenty to fifty percent of women with leiomyomas develop symptoms including abnormal bleeding, pelvic pain and pressure, urinary frequency, reduced fertility and miscarriage. Leiomyomas represent the leading indication for hysterectomy in the United States. The development and severity of symptoms is related to the size and position of the tumors. The proliferation of uterine leiomyoma cells exceeds the limited number of cells undergoing apoptosis resulting in tumor enlargement. Studies from our laboratory have demonstrated the effectiveness of a cytotoxic gene therapy approach known to induce apoptosis to reduce leiomyoma proliferation and volume using human leiomyocytes and leiomyoma cells derived from the Eker rat strain (ELT-3 cells). A strong bystander effect was demonstrated where transfection of a small percentage of leiomyoma cells was able to mediate marked cellular death of the non transfected cells and in vivo tumor regression of uterine leiomyomas. In vitro experiments using the dietary triphenolic stilbene resveratrol, an estrogen alpha receptor antagonist, inhibited proliferation of the ELT-3 uterine leiomyoma cell line in a hypoestrogenic environment. Uterine leiomyomas generally exhibit minimal apoptosis despite evidence that cellular mediators of both the intrinsic and extrinsic pathways of apoptosis are expressed. The anti-apoptosis factor Bcl-2 is highly expressed in leiomyoma cells in comparison to normal myometrium. Bcl-2 protein expression is reduced by estrogen exposure and increased by progesterone exposure. GnRH agonists administered in vivo cause a marked reduction in leiomyoma size without evidence of apoptosis. In contrast, in vitro exposure of leiomyoma cells to GnRH agonists causes marked apoptosis and induction of Fas and Fas ligand. We propose the following Specific Aims: Specific Aim I: To study the effect of HSV-tk/ganciclovir, the dietary ER-alpha receptor antagonist resveratrol, and GNRH agonist on cell proliferation and apoptosis in ELT-3 and human leiomyoma cells. Specific Aim II: To study the effect of HSVtk/ ganciclovir, the dietary ER-alpha receptor antagonist resveratrol, and GNRH agonist on cell proliferation and apoptosis in the ELT-3/nude mouse model of leiomyoma. Specific Aim III: To study the effect of HSV-tk/ganciclovir, the dietary ER-alpha receptor antagonist resveratrol and GNRH agonist on cell proliferation and apoptosis in a human leiomyoma xenograft model. A detailed understanding of the apoptosis and cell survival pathways active in uterine leiomyomas will allow us to better promote long term tumor regression in response to evolving minimally invasive therapies in development for uterine leiomyomas including vascular embolization, high intensity focused ultrasound, and evolving targeted molecular and pharmacologic therapies.